Advisers to the Food and Drug Administration are meeting today to discuss problems with the latest technology to keep blood flowing to the heart. At issue is a new kind of stent developed several years ago. Like older stents, it's used to keep an artery open once doctors have unblocked it. But now there's evidence that these new stents, which are coated with drugs, can cause blood clots.
New technologies have helped many patients avoid coronary bypass surgery. But each advance has brought its own problems.
Michael Domanski, a cardiologist at the National Institutes of Health, says that more than 20 years ago, doctors discovered they could thread a tiny balloon through the arteries to reach an area that was blocked.
"The idea was to try without opening someone's chest to get the same effect," Domanski says, "and in fact, it's been hugely successful."
But early on, doctors realized the balloon angioplasty technique wasn't perfect.
"The problem that frequently occurred was that over time, the blockage would re-accumulate, so that the patient would often need another procedure within the next six months," says Ray Gibbons, a cardiologist at the Mayo Clinic and president of the American Heart Association.
Before long, though, doctors came up with what they thought was a perfect solution: stents, which are tubes made of wire mesh. Gibbons says doctors used angioplasty to widen arteries and then kept them open with stents.
But doctors soon discovered that stents also led to renarrowing of arteries, Gibbons says. "They were less subject to that problem than balloon angioplasty, but it still occurred."
Arteries renarrowed as scar tissue formed around the stent. If there was too much scarring, it could close off an artery. Once again, doctors turned to technology for a solution. Companies began to make stents coated with drugs that would keep scar tissue from forming, called drug-eluting stents. The first model hit the market in 2003, and pretty soon, coated stents dominated the field — even though they cost twice as much. Millions of people are now walking around with drug-coated stents in their arteries.
Michael Domanski of the NIH says the stents have greatly reduced the number of patients who will need to have an artery reopened, but some patients face a new risk, albeit a small one, of sudden clots.
"That's a serious problem because it produces a heart attack and it can produce death," Domanski says.
No one knows for sure why the coated stents cause these blood clots. But doctors are once again looking for a solution. One clue comes from a study at Duke University. Researchers reviewed the medical records of hundreds of people who got drug-coated stents at the medical center there.
All the patients took a drug called Plavix to reduce the chance that clots would form. That's standard practice. But patients who kept taking Plavix longer than six months were far less likely to die or have a heart attack. David Kong, a cardiologist at Duke, says that suggests that long-term use of Plavix could offset the risk of blood clots from coated stents.
"Certainly, the previous recommendations that patients with drug-eluting stents receive Plavix for either three or six months are likely insufficient, given the data we know now," Kong says. Some doctors even think patients with the new stents should stay on Plavix for life.
But FDA advisers meeting this week to discuss new recommendations have no easy answers. Plavix, which can cause internal bleeding, carries its own risks.